Radiation for breast cancer currently mainly consists of full breast radiation, which imparts radiotherapy to the full area of the breast. It necessarily involves surrounding structures such as, but not limited to the heart, lungs, esophagus, chest wall, ribs and other structures that are in close proximity to the breast. A new concept of partial breast radiation targeting the area of the breast involved by cancer is currently gaining popularity. Studies thus far indicate that it is as effective as full breast radiation and eliminates damage to the surrounding organs. Partial breast radiation is currently being delivered through temporarily implanted balloon catheters such as but not limited to the MAMMOSITE or the CONTURA. This process involves placing a radioactive seed or target down the catheter for a brief period of time, over three to five days.
Unfortunately, this method of utilizing a catheter and radioactive seed has a number of drawbacks. Utilizing a concentrated dose of radiation over a short period of time in the form of a radioactive seed planted through means of the catheter or other surgical means creates a multitude of side effects such as fat necrosis, seromas, hematomas, infection and undesirable cosmetic outcomes. When a lumpectomy is performed, a temporary balloon catheter is put into place with the catheter extruding from the breast. This allows an opening into the cavity which increase the chance of infection. Furthermore, this method requires the physician to wait for the pathology report to indicate margins of the specimen to be free of cancer (as well as the absence of cancer from the lymph nodes) before the temporary balloon can be removed and a Mammosite, Contura or other external catheters can be implanted in preparation for partial breast radiation therapy. This sequence of procedures is preferred as soon as possible following lumpectomy. An additional drawback to the catheter methodology is the need to aspirate air from the lumpectomy cavity. Air in a lumpectomy cavity creates “hot spots” or high heat conditions within the cavity when subjected to radiation therapy, thereby causing burns and other undesirable side effects. Accordingly, it is desirable to aspirate or remove the air, most commonly with a syringe and needle. Unfortunately, the current method catheter may be punctured by the needle during aspiration, creating problems for its subsequent use and effectiveness in treatment. These problems are resolved by use of the proposed method. We propose the use of external beam radiation delivered through a multi-directional stereotactic radiation source such as but not limited to the CYBERKNIFE, the BRAIN LAB, and other external beam sources. However, external beam radiation requires a sufficiently identifiable target. Currently, external beam radiation is used on solid organs such as the liver that contains a tumor or the head of the pancreas that contains a tumor whereby a gold seed is implanted in these structures and acts as a guide for focusing the external stereotactic beam. The solid tissue of these organs provides a stable, non-shifting environment for placement of the seed which acts as a target for the external beam source. The use of the catheter in breast tissue has been previously necessary due to the presence of primarily fatty tissue in the breast, precluding a stable environment for placement of a small seed or target. In fatty tissue, a small seed or target would move from the intended target site, rendering the therapy ineffective. The breast is an external structure, constructed primarily of fatty tissue, unlike the other mentioned organs. Consequently, what is necessary then, is a means of stabilizing a seed or other target source within the fatty tissue of the breast, which seed or other target source may then be utilized as a target in a new method of partial breast radiation. The proposed invention addresses this problem. Being an external structure also, the breast is also capable of being more rigidly fixed for targeting in stereotactic radiation machines than the internal organs and is therefore a good candidate for utilizing partial irradiation through careful targeting of the internal implant and/or marker.
U.S. Pat. No. 6,214,045, issued to the applicant, discloses a breast implant of resorbable material sized to replace excised tissue and allowing for in-growth of fibrous tissue to replace the implant. The implant may be elastic, compressible, and expandable and may further contain diagnostic substances. The specification of U.S. Pat. No. 6,214,045 is incorporated by reference herein. Certain diagnostic substances are identified in the '045 Patent as “x-ray opaque or metallic material for identification of the area.” Many embodiments of the implants described in the '045 patent may act as appropriate targets for stereotactic radiation sources as radiopaque targets. Biodegradable materials such as, but not limited to, collagen and other suitably dense biocompatible materials, may be configured suitably radiopaque. The implants may alternatively be constructed of two or more different materials or contain large amounts of air, which will also aid in acquisition and targeting by a suitable stereotactic radiation source. The implant may be shaped spherical to keep the lumpectomy cavity open in a more uniform manner however this is not always necessary as the lumpectomy cavity created by a biopsy procedure can be allowed to partially collapse and conform to the size or shape of the implant. Consequently, the implant shape may guide the external beam source in order to allow a more specific area of the cavity to be radiated on one side or the other, or uniformly circumferentially in the event of utilizing a spherical implant. Particularly when compared with the previously disclosed catheter methodology, the ability to utilize variously shaped implants is superior to the catheter, which is spherically shaped, in the event it is necessary to construct a non-spherical lumpectomy cavity to obtain the desired margins upon removal of the cancer. The implant itself may act as the radio-opaque target or may have added to, more or less, the central portion of the implant, a tiny metallic marker such as but not limited to a gold seed or a titanium seed to further aid as a guide for the external beam. To conform with desired diagnostic needs and procedures, more than one marker may be utilized in a single implant or more than one implant, placed within the lumpectomy cavity. Different marker materials may be contained within a single implant or within more than one implant placed within the lumpectomy cavity. Any metallic material, suitably sterilized, or other relatively dense biocompatible material, may be utilized as a marker within the implant. Where the external beam radiation is utilized, it accomplishes local brachytherapy with its benefits and the beam can be configured over varying time periods so as to eliminate many of the complications associated with the current method of partial breast radiation, the balloon MammoSite or Contura. Use of the implants described in the '045 patent, addresses a multitude of the current problems known to the medical industry such as but not limited to cosmetic deformities, seromas, hematomas, infection and the like while simultaneously providing the stable target necessary for successful targeted radiation therapy. The 045 implants are configured to keep the cavity open and support the surrounding tissue. This is particularly important in radiation therapy as new tissue growth will be inhibited by the presence of radiation therapy. Accordingly, this method and use of the implant will enable the lumpectomy site to retain its configuration throughout radiation therapy and thereafter provide time for regeneration and in-growth of new tissue upon termination of radiation therapy. Once the external beam radiation is accomplished, the implant may biodegrade over a period of time allowing ingrowth of the patient's own natural tissues and, therefore reduce the risk of undesirable cosmetic changes to the overlying skin or the breast. It may also have added to the implant hemostatic agents to minimize bleeding, other metallic markers, oncologic agents, antibiotics and the like.
Another advantage in the use of the implant for targeted partial breast radiation therapy is that the biodegradable implant can be inserted into the breast at the time of the lumpectomy but radiation therapy my be delayed without presenting complications in the maintenance of the targeting means, treatment or to the patient. With the use of the catheter methodology, the externally extruding catheter and its prior discussed issues necessitates immediate radiation therapy treatment to minimize, to the extent possible, potential complications such as infection and discomfort to the patient. Immediate radiation therapy is not always preferred because the surgical wound is fresh and has not healed. The use of radiation further retards healing and promotes seroma formation, infection, and cosmetic defects because of poor healing. The proposed methodology, utilizing the implant, allows the implant to be placed in the lumpectomy cavity and the wound surgically sealed. The patient may maintain a normal lifestyle and radiation therapy may be scheduled as appropriate in the particular case. The patient may undergoe chemotherapy and can delay radiation therapy up to about 120 days without decreasing the therapeutic effects of the radiation. The implant may degrade somewhat over a period of time while the breast is healing to allow the lumpectomy cavity to compress down upon the implant or scar down around the implant shrinking the cavity and stabilizing the target for future radiation. Future radiation therapy may be initiated many days or weeks after the lumpectomy. Radiation therapy may be discontinued, if necessary, and re-instituted as necessary, within the life of the biodegradable implant or, in the case of a marker, at any time thereafter. This accomplishes the prevention of hematomas or seromas, resulting in a better cosmetic outcome while maintaining a stable target for future therapy or diagnosis.